Equipment My first out of air situation

[bipolarbear]

You've got 30 dives, and all your own gear, yet you consider yourself a newbie and you act like one.

Not monitoring your air, not taking the DM's octo when you were already breathing hard were huge mistakes, offering your primary reg to the DM to see if you were doing something "wrong" when you were obviously OOA, completing your safety stop when you AND the DM are BOTH out of air were others, although that last one is on the DM although it's hard to believe there is such a level of incompetence in a supposedly trained professional that would require both of you to make an emergency ascent from safety stop depth and risk an AGE because you just HAD to complete that last 60 seconds of safety stop following a relatively shallow dive. I don't think I've seen this level of combined ineptitude in a single dive.

Where was your dive buddy when all of this was happening?

I think this is unfair on OP.

Based on the the pressure chart the OP has provided (which no one seems to bother reviewing), and the fact that there was no catastrophic gas loss reported, it seems quite clear that what OP experienced was some obstruction / clog in either the valve assembly or the first stage itself. Can be caused by rust, water ingress or other contamination.

We can discount tank roll off (which would have become more breathable as OP shallowed up), free flow / gas rupture and OP inexperience (because as they rightly point out, it's not humanly possible to consume 110 bar from an AL80 i.e. over 1000L of gas in two minutes at 20m).

Agree that safety stop should have been skipped in these circumstances. Also very confused how DM did not have sufficient gas to air share a diver to the surface at the halfway point of a recreational dive. More blame should be attributed to the DM than to the OP here.

OP should have the tanks and first stage inspected. If there is contamination then second stages should probably be looked at also in case some of the particulate has migrated up to the regs.

 

[scubadada]

Hi @ispasov

Did you ever get any information from the operator regarding your incident?

 

[Ken Kurtis]

At about minute 35 I noticed that taking a breath started to require a lot of effort, like something was blocking my hoses. Looking at my computer I saw that I only had 3 BAR left. I immediately went to the dive master and gave him the out of air signal. He understood me and double-checked my computer. He offered me his backup 2nd stage, but I didn't take it immediately, because I was still breathing (harder and harder, but still doable). We slowly started going up.
Here is a photo of the air chart for your reference:

View attachment 914044

I haven't read all the replies so forgive me if I'm going over ground already covered. But a number of things jump out for me. (For those who don't know, I so accident analysis for the L.A. County Coroner so this isn't my first rodeo looking at gear issues.)

All we have is the breathing record but this appears to be a fairly normal dive for the first 35 minutes. OP says he's used about half the tank. Assuming an AL80, he's used 40cf in 30 minutes. Assuming a somewhat constant depth of 22m/66ft (3atm) based on his post, he's using 1.33cfm at depth, which is a surface rate of roughly 0.44cfm. That's pretty good for a "new" diver. A typical newbie rate is more like 0.75cfm (surface rate) in my experience. There's also a weird little downward spike around the 6-minute mark and the 11-minute mark. Not sure what those are.

At the 25-minute mark, it seems there's around 90bar (1,350psi) in the tank and then pretty quickly it goes down to close to 0. But then around the 40-minute mark, the gauge spikes back up to almost 90bar. That it disappeared so quick and that it came back up would seem to favor the valve-not-fully-opened scenario. Simply put, with the valve partially closed, you're sucking air from the hoses faster than the tank pressure can refill it. But I would think with this scenario that you wouldn't get such an abrupt drop in pressure as we can see on the graph. Generally this is going to kick in under 500psi as the tank pressure drops below the reg's IP + ambient pressure that's going to be required to take a breath. OP says he continued breathing on the reg - harder - for a few minutes which might explain why the graph stays low until that spike at the 40-minute mark. That could be where OP goes on the DM octo, tank pressure rises, gauge reflects that. Doesn't explain the almost immediate drop after the spike though.

This is all speculation, based on the OP's statement but some things don't quite seem to line up. (I'm not saying the OP is lying or concealing anything. But the tank and reg would have to be inspected and tested to get any definitive answers. However . . .

What REALLY catches my eye is that this out/low-on-air around the 35-minute mark. The dive seems to end around the 55-minute mark. The first reaction I had was, "WTF????" There is NO excuse/reason (IMHO) for an OOA diver, let alone one tethered to a DM, to continue this type of a dive for another 20 minutes. I don't have an issue with the safety stop. But from 22m/66ft, even at a normal ascent rate, you're on the surface in no more than 2 minutes. So they should have been on the surface maybe 37 minutes into the dive or at the 40-minute mark if they wanted/needed to do a 3-minute safety stop, not 55-minute in.

I've got a big problem with this part of it because it says to me that the DM isn't reacting properly to the situation. Now perhaps I'm missing something here so if the OP reads this, feel free to fill me in. But extending the time underwater once you've got the low/out situation doesn't add to anyone's safety and certainly would seem to increase the risks of the dive.

 

[Nemrod]

I am not going to read all of these pages now, busy working on something. But a cursory read through, this sounds very similar to the OOA incident I had last November which was caused by the sintered filter being nearly fully clogged with the remains of an O-ring. I could occasionally get a sip of air. Enough to get to the surface and even do a safety pause given it was the fourth dive of the day. Was I air stressed, yes, very much so. And it was a night dive and no buddies around, they off chasing another octopus or something . When it first happened I could get virtually nothing and it happened pretty suddenly after going head down to get a shot of, yes, an octopus! I began to mosey on up and along the way I was able to get an occasional partial breath. My cylinder had plenty of air back on the boat.

If it has not been done already, this regulator needs to be inspected and serviced. Paying particular attention to the sintered filter for particulate debris. Another possibility, diaphgram regulators especially, do not like having water shoved through them. It can result in hydraulic lock. The water would have had to be in the cylinder as would any other FOD. The dip tube could have been missing or unscrewed. Weird.